Alntraet -The performance ofa cocurrent downtlow contactor (CDC) bubble column reactor has been examined using a fnst order reaction involving the palladium catalyzed hydrogenation ofitaeonic acid. The reaction was carried out at ambient t~aturΒ’ and in the pressure range 110-290 kPa using 5% and 10% w/w Pd/charcoal catalysts in two solvents (water and 2propanol). The quataitative evaluation of the mass transfer and kinetic parameters was achieved using the classical film model for a lust-order reaction.
Because of the large speetic gas-liquid interracial area generated in the CDC, kLa, the volumetric gas-liquid mass transfer coefficient, was large (0.4-6 s 4) and was comparable with that of a much smaller stirred reactor (-1/10 in size) with only -10% of the latter's energy consumption. Unlike conventional bubble columns where the gas-liquid mass transfer is otten the rate limiting step for this type of reaction, the relative contribution of the gas-liquid mass transfer resistance in the CDC was low (1 -50% of the total resistance) compared with the liquid-solid mass transfer and surface reaction resistances for the three-phase catalytic hydrogenation ofitaconic acid.
The liquid-solid mass transfer coefficient (k,) and ftrst-order reaction rate constant (k~) in the CDC were similar to those obtained in the stirred reactor with both the liquid-solid mass transfer and surface reaction being important rate steps.
However, the magnitude of k, and k~ depends critically on the method of calculating k, and an independent evaluation of k, should be carried out to obtain more accurate k~ values. These initial studies indicate that the CDC has good potential as a three phase catalytic reactor and unlike some bubble columns can be used for relatively fast reactions.